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STS51L Accident Questions



 
 
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  #1  
Old February 15th 05, 02:20 AM
Mark Percival
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Default STS51L Accident Questions

As it is known, the left SRB burned through the o-ring at the side facing
the ET causing the accident. Then I started to wonder.

Would it have been possible for the o-ring to burn through on the other
side of the SRB (ie: away from the tank)? Was it just bad luck it burned
through where it did?

If the above is possible then what would the effect had been on the
remainder of the rise to orbit? Would the Challenger been destroyed
anyhow?

If not then would have one of the abort modes been called after SRB
burnout? How bad would the gasses leaking pushed it off course?

Mark Percival
Montreal, Quebec
  #2  
Old February 15th 05, 03:15 AM
Ed Kyle
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another scenario for an outward-facing breach is that eventually the

breach would have weakened the entire field joint to the extent that

it
would fail altogether, which also would have resulted in stack

breakup.

This is what I think would have happened. The stack broke up at 73
seconds, only
15 seconds after the first flame appeared at the joint. The SRB would
have had to hold together for another 47 seconds to make it.

- Ed Kyle

  #3  
Old February 15th 05, 05:27 AM
Pat Flannery
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Jorge R. Frank wrote:

Hard to say. The SRBs and SSMEs were clearly trying to compensate for the
loss of thrust from the RSRB when the stack broke up. It's possible that if
the breach had not gotten much worse, the gimbals would still have been
able to control it. On the other hand, if the breach had gotten worse, it
could have exceeded the control authority of the gimbals and the stack
would have tumbled and broken up.




If burning had started between the exterior of the fuel grain and the
inside of the SRB casing due to the breach, that also could have caused
the SRB to break up, as the gas being generated could debond the fuel
grain from the casing, or cause it to fracture- leading to uncontrolled
burning and excessive pressures in the casing. When solids fail that way
the result is generally a big explosion in a matter of a few seconds.

Pat



Pat
  #4  
Old February 15th 05, 03:35 PM
Daydreamer99
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I'm not an expert. lets down scale this to model rocketry. If
the area where the O ring was compromise the leak or explosion could
have taken place anywhere. If I remember correctly the SRB where
manufacture and shipped in pieces to cut costs. No problem...The
problem is basic plumbing you need a compression fit with the O ring.
I think this would have decrease the change of the accident from
happening.

Also everyone under pressure to meet time and cost restrictions.
NASA is Safe but sometime you have to gamble. The shuttle is a
proven.........We need a ship assemble like the space station in
orbit.......This will cut cost.

  #5  
Old February 15th 05, 05:22 PM
Pat Flannery
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Daydreamer99 wrote:

I'm not an expert. lets down scale this to model rocketry. If
the area where the O ring was compromise the leak or explosion could
have taken place anywhere.



The area where it failed at was the one that got a great deal of stress
put on it during the "twang"- when the shuttle makes the rest of the
launch stack bend as its engines are ignited before SRB ignition. The
area of the SRBs astern of the aft attachment point to the ET undergo
the most stress during this event; and indeed film of the Shuttle on the
pad showed a jet of smoke emerging from the the field joint that would
later burn through on SRB ignition and prior to lift-off. This was due
to the O-rings on that field joint being unseated by the "twang" and
unable to reseat themselves due to their low temperatures making them
inflexible.

Pat

  #6  
Old February 16th 05, 09:34 PM
Henry Spencer
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In article ,
Mark Percival wrote:
Would it have been possible for the o-ring to burn through on the other
side of the SRB (ie: away from the tank)? Was it just bad luck it burned
through where it did?


Not entirely just bad luck. The SRB rear attach struts put extra stress
on that area of the casing, tending to pull the joint farther open there.
Transient loads from the struts during ignition probably contributed to the
initial leak and likely O-ring damage there; transient loads during
windshear shortly before the accident probably re-opened the leak.

The joint design was generally a poor one, with margins particularly thin
in the conditions of that launch, and a leak could have happened anywhere,
but that particular area was predisposed to it.

If the above is possible then what would the effect had been on the
remainder of the rise to orbit? Would the Challenger been destroyed
anyhow?


Had the leak been elsewhere, there would have been some chance of
survival. The **** hit the fan not because of the leak itself, but
because of the stream of hot gas playing on the attach struts and the ET;
more or less simultaneously, (a) the struts failed and the SRB pivoted
around its forward attachment, so its nose mashed in the side of the ET,
and (b) the ET aft dome tore loose. So the ET disintegrated, and the
orbiter was thrown violently out of control at Mach 3 and broke up. The
failing SRB stayed pretty much intact until Range Safety blew it up some
seconds later.

If the struts had held and the ET not been exposed to excessive heat, the
SRB would have stayed in one piece for a while, perhaps long enough. If
the leak was in a position where it didn't damage the orbiter wing, then
there could have been problems with side thrust from the leak, and from
forward thrust falling off because of the gas lost to the leak (the
shuttle can't cope with any substantial difference in thrust between the
two SRBs), but there was a chance.

If not then would have one of the abort modes been called after SRB
burnout? How bad would the gasses leaking pushed it off course?


Hard to say. It might even have been possible to carry on to orbit.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |
  #7  
Old February 17th 05, 06:09 AM
Charleston
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"Pat Flannery" wrote:

snip

and indeed film of the Shuttle on the pad showed a jet of smoke emerging
from the the field joint that would later burn through on SRB ignition and
prior to lift-off. This was due to the O-rings on that field joint being
unseated by the "twang" and unable to reseat themselves due to their low
temperatures making them inflexible.


Kind of like this unreleased STS 51-L video where the smoke, uh stops at
3.375 seconds?

http://www.challengerdisaster.info/s..._m-2_mpg_i.mpg

Daniel


  #8  
Old February 17th 05, 07:22 PM
Pat Flannery
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Charleston wrote:

Kind of like this unreleased STS 51-L video where the smoke, uh stops at
3.375 seconds?

http://www.challengerdisaster.info/s..._m-2_mpg_i.mpg



You know, there's a far better video of the smoke plume out there than
that; in fact, I can't even see the smoke plume in that crappy and
distorted video. The other video is in color in color and a _lot_ closer up.

Pat
  #9  
Old February 18th 05, 12:33 AM
Herb Schaltegger
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In article ,
Pat Flannery wrote:

Charleston wrote:

Kind of like this unreleased STS 51-L video where the smoke, uh stops at
3.375 seconds?

http://www.challengerdisaster.info/s..._m-2_mpg_i.mpg



You know, there's a far better video of the smoke plume out there than
that; in fact, I can't even see the smoke plume in that crappy and
distorted video. The other video is in color in color and a _lot_ closer up.

Pat


Which is probably one reason why this particular footage was
"unreleased," along with the fact that due to the angle of the camera
with respect to the trajectory and orientation of the stack
immediately prior to and following breakup, you can't really see much
that you can't see from much better perspectives elsewhere.

--
Herb Schaltegger, B.S., J.D., GPG Key ID: BBF6FC1C
"The loss of the American system of checks and balances is more of a security
danger than any terrorist risk." -- Bruce Schneier
http://dischordia.blogspot.com
http://www.angryherb.net
  #10  
Old February 18th 05, 04:19 AM
Charleston
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"Pat Flannery" wrote:
Charleston wrote:

Kind of like this unreleased STS 51-L video where the smoke, uh stops at
3.375 seconds?

http://www.challengerdisaster.info/s..._m-2_mpg_i.mpg


You know, there's a far better video of the smoke plume out there than
that; in fact, I can't even see the smoke plume in that crappy and
distorted video. The other video is in color in color and a _lot_ closer
up.


There is definitely better film of the smoke puffs that occured immediately
at launch, that is true (film cameras E-60, E-63). Subsequently that film
was transferred to video. The best motion picture film photography of the
smoke puffs at launch, that is the cameras positioned with a direct angle to
observe the start-up tranisent as to location, direction of smoke, size,
etcetera, all failed to operate! The odds of that failure being coincidence
are dim, but it did happen that way.

As for your inability to see the smoke, please don't blame me. It takes a
lot of bandwidth to put up MPEG II or AVI. I will put up some higher
resolution photography later tonight for a limited timeframe. Personally, I
can see plenty of black smoke up to about 3.4 seconds, and subsequently I
see significant diffuse smoke brightly illuminated by the light of the SRB
flames. Also, I conclude that the "STS 51-L JSC Visual Data Analysis
Sub-Team" and the team at LMSC got it right when they saw smoke and "solid
material" as late as 45 seconds emanating from the same region of the
vehicle. Unfortuantely, they were overruled by the film team at KSC. As
you probably know, it is KSC's views that are reflected in the final
Presidential Commission report.

Daniel


 




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